Pianotech

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.

Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

If that were true, then threads like this wouldn't exist.
-chris

Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.

Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

I believe the issue is primarily that some individuals are striving for relevance, although I personally am focused on following Nick Gravagne's Sage advice and reducing my neurotic tendencies. I suppose I'll have to be satisfied with that.

The problem, Chris, is that no technicians use units of inertia, not even those capable of understanding it. Even individuals like the late Darrell Fandrich and certified engineer John Rhodes developed a concept unrelated to units of inertia, but rather something simpler using static measurements  

David Stanwood's system, which many people utilize, also derives inertia from a series of static measurements. His objective is to achieve a specific inertia target by combining data such as front weight, strike weight, action leverage, and balance weight. These parameters, when met according to his system, result in a manageable level of inertia. It's worth noting that pianos inherently have higher inertia in the bass due to the decreasing mass of the hammers, but that's a separate issue. As a side note, for those interested in achieving a uniform level of inertia, it might be worth considering the addition of lead weights at opposite positions and equal values on the front and back of the keys to increase key inertia. However, currently we tend to use the minimum number of weights necessary to attain a specific balance weight. Consequently, the contribution of the key to the overall inertia is less significant compared to leverage and hammer mass.

Therefore, we aim for specific strike weights with certain action ratios to achieve an acceptable level of inertia. If you're unfamiliar with the process, you can become a Stanwood licensed installer to learn and apply these techniques, which can be valuable credentials in the market. David Stanwood and others, including myself, have been generous in sharing this information and offering a practical approach without delving into relatively useless numerical calculations of inertia.

While I appreciate your desire to demonstrate your engineering expertise, it holds little practical importance in what we actually do.

If that were true, then threads like this wouldn't exist.
-chris

Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.

Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

I believe the issue is primarily that some individuals are striving for relevance, although I personally am focused on following Nick Gravagne's Sage advice and reducing my neurotic tendencies. I suppose I'll have to be satisfied with that.

The problem, Chris, is that no technicians use units of inertia, not even those capable of understanding it. Even individuals like the late Darrell Fandrich and certified engineer John Rhodes developed a concept unrelated to units of inertia, but rather something simpler using static measurements  

David Stanwood's system, which many people utilize, also derives inertia from a series of static measurements. His objective is to achieve a specific inertia target by combining data such as front weight, strike weight, action leverage, and balance weight. These parameters, when met according to his system, result in a manageable level of inertia. It's worth noting that pianos inherently have higher inertia in the bass due to the decreasing mass of the hammers, but that's a separate issue. As a side note, for those interested in achieving a uniform level of inertia, it might be worth considering the addition of lead weights at opposite positions and equal values on the front and back of the keys to increase key inertia. However, currently we tend to use the minimum number of weights necessary to attain a specific balance weight. Consequently, the contribution of the key to the overall inertia is less significant compared to leverage and hammer mass.

Therefore, we aim for specific strike weights with certain action ratios to achieve an acceptable level of inertia. If you're unfamiliar with the process, you can become a Stanwood licensed installer to learn and apply these techniques, which can be valuable credentials in the market. David Stanwood and others, including myself, have been generous in sharing this information and offering a practical approach without delving into relatively useless numerical calculations of inertia.

While I appreciate your desire to demonstrate your engineering expertise, it holds little practical importance in what we actually do.

If that were true, then threads like this wouldn't exist.
-chris

Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.

Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

-chris

Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   

Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

-chris

John,
I would check soundboard crown. The lack of crown can be a major factor contributing to lack of dynamic range. Also, check for down bearing.

Friction is low in this action. If I remember correctly C4 had 8g. Hammers we tested had 10 or more swings.

As to that wippen rail, yes, we should check the spread. Does anyone have a number on how wide the spread should be on an SD1 or a method for deriving it?

As to hammers being too light and feeling heavy, that's a new one to me. Would anyone care to elaborate?

Friction is low in this action. If I remember correctly C4 had 8g. Hammers we tested had 10 or more swings.

As to that wippen rail, yes, we should check the spread. Does anyone have a number on how wide the spread should be on an SD1 or a method for deriving it?

As to hammers being too light and feeling heavy, that's a new one to me. Would anyone care to elaborate?

John,

What is the knuckle to center pin measurement? If it's less than 16mm you've got trouble.

How does the jack line up under the knuckle at ideal rest position...is it a perfect 90° angle? This is the first place to look to determine if the spread is correct or not.

What is the condition of whippen contact cushion? Indented, corroded, etc? If so, clean with starting fluid, brush with a wire brush, then apply a small amount of VS-PROFELT. Then bolster one with bushing cloth and see if there's any difference. 

Peter Grey Piano Doctor 

Friction is low in this action. If I remember correctly C4 had 8g. Hammers we tested had 10 or more swings.

As to that wippen rail, yes, we should check the spread. Does anyone have a number on how wide the spread should be on an SD1 or a method for deriving it?

As to hammers being too light and feeling heavy, that's a new one to me. Would anyone care to elaborate?